In a typical electrostatographic reproduction apparatus, a photoconductive imaging member has a uniform charge applied to it. The member is then imagewise exposed to light to selectively discharge the member through a grounded conductive layer, leaving behind an electrostatic latent image, corresponding to information to be reproduced, on the photoconductive member. This latent image is developed with toner particles from a two-component developer to form a visible image. The visible image is transferred to a receiver sheet to which the visible image is permanently fixed by fusing it with heat and/or pressure.
To prepare the photoconductive imaging member for the next copying cycle, the member is cleaned to remove debris such as residual toner particles and paper dust, and to cure film damage incurred during the transfer step. Cleaning of the photoconductive member may be performed, for example, with a magnetic brush. Such a magnetic brush includes a core composed of a series of radially mounted, alternating pole magnets. The magnets are surrounded by a cylindrical shell made of a nonmagnetic, conductive material. Relative movement is provided between the core and the shell by rotating the core and/or the shell. Magnetic carrier particles, preferably similar to carrier particles used in the two-component developer, are applied to the surface of the shell. The carrier particles adhere to the shell due to the carrier particles attraction to the magnetic core. In addition, the carrier particles, under the influence of the alternating pole magnetic fields, tumble about the surface of the shell.
The photoconductive member is cleaned by being contacted with the mass of tumbling carrier particles. The carrier particles remove residual toner particles and also abrade the outer surface of the photoconductive member to effect cleaning. The degree of abrasion is important in determining proper preparation of the photoconductive imaging member. If not enough wear of the photoconductive member is accomplished, the photoconductive member will not be effectively cleaned. This will result in image artifacts on subsequent copies created on the electrostatographic reproduction apparatus resulting in poor quality copies. On the other hand, if too much wear is imposed, the photoconductive member's life span will be greatly reduced. This will necessitate changing the photoconductor more frequently, resulting in higher operating costs for the reproduction apparatus.
The above described excessive wear occurs when small sized carrier particles are used to clean the photoconductive imaging member. However, if larger sized particles are used, the photoconductive imaging member becomes scratched and thus damaged. This will result in image artifacts on output copies.